Not Applicable
Not Applicable
1. Field of Invention
The invention relates in general to spacecraft and aerospace plane, in particular, to fly back boosters that can be recovered after use, to reusable launch vehicles that can go to and come back from Earth orbits, and to aerospace vehicles that can fly at hypersonic speed in the air and/or go to and come back from Earth orbits.
2. Description of Prior Art
Fly Back Booster
Most existing designs of fly back boosters are based on configurations of fixed wings with fixed sweep angles. These fixed wings stick out from the fuselages of fly back boosters thus limit the flexibility of forming different launch configurations by connecting a fly back booster with other fly back booster(s) and/or other vehicle(s). In addition, most designs of fixed-wing fly back boosters choose wings with low aspect ratio. A fly back booster with wings of low aspect ratio requires relatively high engine thrust to fly at low speed, has high landing speed, and needs long runway for landing because this kind of wings have low lift-to-drag ratio (L/D) at low speed.
U.S. Pat. No. 6,450,452 xe2x80x9cFly Back Boosterxe2x80x9d issued to R. Spencer et al invents a fly back booster having a pair of fixed wings and a pair of canards. As the fixed wings stick out from the fuselage of the fly back booster, they prevent the fly back booster from having a lot of ways to connect with other fly back booster(s) and/or other vehicle(s) to form different launch configurations.
Shown at page 32 of the Sep. 16, 2002 issue of Aviation Week and Space Technology, Northrop Grumman proposed a fly back booster having a pair of foldable fixed wings. The fixed sweep angle, low aspect ratio wings are folded when the fly back booster is connected to a core vehicle. After the fly back booster is separated from the core vehicle, the folded fixed wings are unfolded so that they can make the fly back booster fly back. This design increases the booster""s weight not only by adding a folding/unfolding system but also by increasing the wings"" structural weight because the structures of foldable wings are not continuous thus are heavier than wings that are not foldable. Had the extra weight of the foldable wings been saved, either higher orbital height or more payload can be achieved.
Besides designs based on fixed wings with fixed sweep angles, U.S. Pat. No. 5,031,857 issued to I. MacConochie et al invents a fly back booster having a variable oblique wing. When being connected to other vehicle(s), the fly back booster""s oblique wing is yawed to be generally parallel with the longitudinal axis of the fly back booster. By this way, the fly back booster is very flexible to form different launch configurations by connecting with other fly back boosters and/or other vehicles. However, oblique wing has inherent aerodynamic disadvantages that may prevent it from being used on fly back boosters. The major shortcoming is stability and control problem of oblique wings. That is, when the oblique wing is yawed at an angle so that half of the oblique wing becomes a swept-forward wing and another half becomes a swept-back wing, the roll control and pitch control of the fly back booster is coupled, making it difficult to control and maintain stability. For example, suppose the wing is yawed to an angle so that the right side of the wing becomes a swept-forward wing, the left side of the wing becomes a swept-back wing, and the fly back booster uses ailerons or flaperons to achieve roll control. When the fly back booster needs to bank to the left, it will make an unexpected nose-up movement while banking to the left. On the country, when the fly back booster needs to bank to the right, it will make an unexpected nose-down movement while banking to the right. This inherent problem makes oblique wing difficult to be used on fly back boosters.
Reusable Launch Vehicle
The Space Shuttle currently being used in the United States has a pair of fixed sweep angle, low aspect ratio wings. These wings do not give the Space Shuttle good performance at low speed and landing. For example, the touchdown speed of the Space Shuttle is 341 km/h (212 mph) to 363 km/h (226 mph) when the Space Shuttle has a landing weight of 104, 328 kg (230,000 lb). In contrast, the approach speed of Boeing 747 is 284 km/h (176 mph) even though the Boeing 747 has a landing weight of 260,360 kg (574,000 lb).
Shown at page 32 of the Sept. 16, 2002 issue of Aviation Week and Space Technology, Northrop Grumman proposed a concept of a fixed-wing reusable launch vehicle (the core vehicle). The sticking out fixed sweep angle fixed wings of the reusable launch vehicle limit the ways to connect boosters onto the reusable launch vehicle and force the boosters to have foldable wings that are heavy and complex.
Shown at page 28 of the Apr. 1, 2002 issue of Aviation Week and Space Technology, Northrop Grumman and Orbital Science proposed a concept of launching a fixed sweep angle fixed-wing reusable launch vehicle from the back of a flying aircraft. As shown in the picture on this page, the fixed-wing reusable launch vehicle has a pair of low aspect ratio wings and is mounted on the back of a flying wing type aircraft that can fly at subsonic speed. Right after separated from the aircraft, the reusable launch vehicle with low aspect ratio wings will have lower lift-to-drag ratio thus needs higher propulsion energy to generate enough lift than a reusable launch vehicle with high aspect ratio wings. If there is a kind of wings that can have high lift-to-drag ratio (L/D) at both low and high speed, some of the propulsion energy used to generated enough lift can be saved to accelerate the reusable launch vehicle to achieve higher orbit height or more payload.
U.S. Pat. No. 6,119,985 issued to M. Clapp invented a reusable launch vehicle having air-breathing engine(s) so that it can horizontally take off like an aircraft, has its oxidizer tank(s) filled by another aircraft in the mid-air, and fly to Earth orbit with its rocket engine(s). Shown in the patent, the reusable launch vehicle also has a pair of fixed sweep angle, low aspect ratio wings, The low lift-to-drag ratio (L/D) feature of these wings at low speed makes the reusable launch vehicle needs relatively high engine thrust and high fuel consumption to take-off and climb to high altitude in the air. If there is a kind of wings that can have high lift-to-drag ratio (L/D) at both low and high speed, the reusable launch vehicle can use smaller thus lighter air-breathing engine(s) and save more fuel for the rocket engine(s) to achieve higher orbital height or carry more payload.
U.S. Pat. No. 6,029,928 issued to M. Kelly invents a reusable launch vehicle that is towed by an aircraft to take-off horizontally and to reach an altitude in the air like a glider. After separates from the towing aircraft, the reusable launch vehicle accelerates and flies to Earth orbit on its own engine(s). In order to have satisfied aerodynamic performance for both gliding and high speed flying, the invention uses lifting surfaces like large delta wings, variable sweep wings, and variable X-wing that has a pair of high speed wings and a pair of low speed wings. However, both the large delta wings with big wing area and variable sweep wings are heavy, making the reusable launch vehicle less efficient. The variable X-wing is easy to cause unstable conditions when it is being rotated to switch between the high speed wings and low speed wings, making it difficult to be used on reusable launch vehicles. The above analysis indicates that Kelly""s invention needs a kind of wings that is not heavy, and can have high lift-to-drag ratio (L/D) at both low speed and high speed.
Aerospace Plane
Shown at page 40 of the Jan. 28, 2002 issue of Aviation Week And Space Technology and page 81 of the Sep. 9, 2002 issue of the same magazine, the configurations of aerospace planes like X-43 and HyperSoar are mainly designed to optimize hypersonic performance of the aerospace plane but has sacrificed its low speed performance. Both X-43 and HyperSore mainly use a flat fuselage with very low aspect ratio to generate lift. Although they have a pair of wings at the tail of the fuselage and may have a pair of canard, they are also of low aspect ratio. This kind of low aspect ratio configurations has low lift-to-drag ratio (L/D) at low speed, making the aerospace plane need long runway to take-off and land, has high fuel consumption while flying at low speed, and reguire high engine thrust thus bigger engine(s) to take-off, climb and accelerate to its cruising altitude, and land. If the aerospace plane has a kind of wings that have high lift-to-drag ratio (L/D) at subsonic, transonic, and supersonic speed without deteriorating its hypersonic performance, it will have greater flexibility, longer range, and higher payload capability.
The fundamental object and advantage of my invention is to make a spacecraft and an aerospace plane that can efficiently, effectively, and flexibly fly at a wide range of speed. Specifically, the objects and advantages of a spacecraft and aerospace plane based on my invention are:
A scissors wings configuration for spacecraft and aerospace planes has been invented to achieve the above-mentioned objects and advantages. The scissors wings consist of two continuous, generally straight main wings rotatably installed on the fuselage of a spacecraft or an aerospace plane via one or two hub device(s) like pivot(s) or hollow turret(s). Both of the main wings can have control surfaces like ailerons, lift-generating devices like flaps, and other devices. Both of the main wings can be turned or yawed at opposite directions with generally the same yaw angle.
One way to install the main wings is to have one main wing mounted above or at the upper part of the fuselage of the spacecraft or aerospace plane and another mounted beneath or at the lower part of the fuselage. The second way to install the main wings is to mount both of the main wings above or at the upper part of the fuselage with one main wing over another. Similarly, the third way to install the main wings is to mount both of the main wings beneath or at the lower part of the fuselage with one main wing over another. The fourth way to install the main wings is to mount both of the main wings at around the middle part of the fuselage with one main wing over another.
The following paragraphs explain how can the invention achieve the above-mentioned objects and advantages:
First, if spacecraft are launched vertically like the Space Shuttle, the invention can make them flexibly form different launch configurations by connecting with other vehicles. When a spacecraft is at vertical launch position, both of the main wings are yawed or turned so that their long axes are generally parallel with the longitudinal axis of the spacecraft""s fuselage. By this way, the spacecraft does not have main wings that stick out to prevent it from connecting with other vehicles.
Second, if spacecraft and aerospace planes take-off like aircraft or gliders, the invention can make them achieve good horizontal take-off performance. During horizontal take-off, both of the main wings are yawed to be either generally perpendicular to the longitudinal axis of the fuselage of a spacecraft or aerospace plane or only have small sweep angles. By this way, the main wings can have high aspect ratio to achieve high lift-to-drag ratio (L/D) at low speed, making the spacecraft or aerospace plane able to become airborne at relatively low speed with low engine thrust or towing force.
Third, if spacecraft and aerospace planes are carried or towed to be airborne and launched in the mid-air, the invention can help them smoothly separate from the aircraft carrying or towing them and quickly achieve steady and sustainable flying condition after the separation. No matter the separation occurs at subsonic or supersonic speed, a spacecraft or aerospace plane can adjust the yaw angle of its main wings to have an optimized aerodynamic character for the separation and then quickly adjust the yaw angle to fly on its own.
Forth, the invention can make spacecraft and aerospace planes achieve efficient climb and acceleration in the air at subsonic, transonic, and supersonic speed after their horizontal take-off or horizontal launch. A spacecraft or aerospace plane with scissors wings only needs relatively low engine thrust and low fuel consumption during its climb and acceleration in the air because it can maximize its lift-to-drag ratio (L/D) at a wide range of speed by adjusting the yaw angle of its main wings. This efficiency can save fuel for longer range, higher orbital height, or more payload.
Fifth, during the return flights of spacecraft and aerospace planes after they finish their space or hypersonic flights, the invention can make them achieve efficient and effective controlled flight in the air at supersonic, transonic, and subsonic speed. Also due to scissors wings"" ability to maximize lift-to-drag ratio (L/D) at a wide range of speed, a spacecraft or aerospace plane with scissors wings can have better gliding performance, needs smaller engine(s), and consumes less fuel during its return flight than the ones with other aerodynamic configurations like low aspect ratio wings.
Sixth, the invention can make spacecraft and aerospace planes achieve good landing performance. During landing, both of the main wings are yawed to be generally perpendicular to the longitudinal axis of the fuselage of a spacecraft or aerospace plane or only have small yaw angle. By this way, the spacecraft or aerospace can have a high aspect ratio configuration to achieve low approach speed. The low approach speed makes it land on short runways, have lightweight landing gears because the impact load for touchdown is also low, and have lighter breaks on landing gears.